Named Game of the Year by over 50 publications, Valve's début title blends action and adventure with award-winning technology to create a frighteningly realistic world where players must think to survive. Also includes an exciting multiplayer mode that allows you to play against friends and enemies around the world.

A short explanation how to implent this into your own mods or customize it futher would be nice. I've started the mod but the achivements didn't even work; at least "swinging the crowbar" didn't. Havn't bothered killing 100 headcrabs, yet hehe.